Despite unrelenting heat last week, locals raised their thermostats and shut off the lights last week, slicing about 1.4 percent off the peak power use, utility officials said this week.

As temperatures climbed into the nineties and triple digits, utilities wanted some insurance against possible brownouts, especially without any of the 2,200 megawatts of power from the disabled San Onofre Nuclear Generating Station. San Diego Gas & Electric Co., Southern California Edison, and the California Independent System Operator, a regulator of the grid, called for conservation. Residents and businesses took advantage of an assortment of incentives to cut their use.

"It's better than what we forecasted," said Michelle Costello, demand response manager for SDG&E. She would later add, "In some ways it is a drop in the bucket. We factor these forecasts and these amounts into our overall plan for our resource in our region."

Residents and businesses in SDG&E territory reduced peak load by 53 megawatts on Thursday and Friday, cutting 1.3 percent off the peak load of about 4,400 megawatts, Costello said.

And the California Independent System Operator, which manages supply and demand for most of California, said the state cut 900 megawatts from peak demand, or 1.9 percent, on the days it called
a Flex Alert
, a voluntary conservation program.

A megawatt of power is enough to supply 650 typical Southern California houses. Reducing the load by 900 megawatts is almost equivalent to removing the Encina Power Station in Carlsbad from the grid.

Stephanie McCorkle, a spokeswoman for the operator, said Flex Alerts typically inspire 750 to 1,000 megawatts of electricity savings.

The operator maintains a minimum power reserve of 7 percent of total load, or about 50,000 megawatts during peak power periods. The operator calls a Flex Alert if it's concerned about reserves. If reserves drop below 7 percent, it can call a series of more intense alerts that call for more conservation.

In 2001, during the second year of California's power crisis, when rolling blackouts were a real threat, the state and utilities used demand-response programs to power consumption by an average of 5.75 percent each summer month, according to
a 2002 study
from the Lawrence Berkeley National Lab.

"This is a heat wave. This is not a crisis," said
Scott Anders
, director of the Energy Policy Initiatives Center at University of San Diego. "Pushing the Flex Alert button, just doing that gets you 2 percent, it would be interesting over time to see if that holds up. That's what we're trying to figure out if you push that button."

The utilities use a host of programs to provide financial incentives for conservation, whether they're credits to a future electric bill or penalties for using too much power. Choosing when to activate those programs requires a committee within the utilities of people with expertise in generation, reliability, and the programs themselves.

"We have actually a whole host of different triggers," Edison's Wood said. "Some are based on reliability, grid conditions, some are based on economic and load and weather conditions."

Fro residents, Edison has a program called "
Save Power Days
." The utility will call such a day 24-hours in advance. When the program kicks in, enrolled customers who reduce their power consumption that day will get bill credits. The utility called the program twice last week, Wood said.

"We're trying to make sure that it's fully functional," she said. "We want to make sure things are going well, we will eventually use it more often."

SDG&E has the very similar "Reduce Your Use" program, though all residential customers are automatically enrolled.

The utility called four "
Reduce Your Use
" days in the last week, and on each day about 500,000 of its 1.4 million customers participated. They had an average bill credit of $2, or about 2.7 kilowatt hours. A typical house uses 16.7 kilowatt-hours a day, so participating residential customers reduced their load by 16.2 percent on each day.

Still the utility doesn't want to call such days all the time.

"We don't want to frustrate customers," Costello said.

Correction: This story said San Onofre produced 4,400 MW of power. It produces 2,200 MW. We apologize.